From the past, when electronic components are soldered to a prescribed surface of a printed circuit board, a wave soldering apparatus is often used. On a wave soldering apparatus, a jetting apparatus which jets molten solder to a printed circuit board is mounted. As shown in the Patent Documents 1 to 3, the jetting apparatus has a duct, a nozzle and a pump. In accordance with the jetting apparatus, the molten solder is sent to the nozzle through the duct by the pump. The nozzle jets the molten solder having a liquid surface level corresponding to the pump output. Thereby, the molten solder jetted from the nozzle makes it possible to solder the electric components to the printed circuit board.
As to a pump mounted on the jetting apparatus described above, a wave soldering apparatus is disclosed wherein the duct is connected to a pump housing over the screw pump and the molten solder is sent from the pump housing to the duct (see Patent Document 3).
In addition, as to a method of jetting the molten solder having the same height from a nozzle, some wave soldering apparatuses are disclosed. In a first wave soldering apparatus, multiple flow-crossing plates bent upward are provided inside of the duct, and the flow direction of the molten solder is compulsory changed from the horizontal direction to the vertical direction directly below the jetting surface (see Patent Document 4). In a second wave soldering apparatus, the top of the duct suspends multiple uniform-flow plates, and the flow direction of the molten solder is compulsory changed from the horizontal direction to the vertical direction directly below the jetting surface (see Patent Document 5). In a third wave soldering apparatus, multiple flow-turning plates bent upward are provided at the bottom of the duct, and the flow direction of the molten solder is compulsory changed from the horizontal direction to the vertical direction directly below the jetting surface (see Patent Document 6).